diff --git a/ports/esp32/boards/GENERIC_D2WD/sdkconfig.board b/ports/esp32/boards/GENERIC_D2WD/sdkconfig.board
index 367283ded3..07e208a09a 100644
--- a/ports/esp32/boards/GENERIC_D2WD/sdkconfig.board
+++ b/ports/esp32/boards/GENERIC_D2WD/sdkconfig.board
@@ -1,3 +1,7 @@
+# Optimise using -Os to reduce size
+CONFIG_COMPILER_OPTIMIZATION_SIZE=y
+CONFIG_COMPILER_OPTIMIZATION_PERF=n
+
 CONFIG_ESPTOOLPY_FLASHMODE_DIO=y
 CONFIG_ESPTOOLPY_FLASHFREQ_40M=y
 CONFIG_ESPTOOLPY_FLASHSIZE_2MB=y